(function($){  
    $.fn.snow = function(options){  
     var $flake = $('<div id="snowbox" />').css({'position': 'absolute','z-index':'9999', 'top': '-50px', 'cursor': 'pointer'}).html('❄'),  
     documentHeight  = $(document).height(),  
     documentWidth   = $(document).width(),  
     defaults = {  
         minSize     : 10,  
         maxSize     : 20,  
         newOn       : 1000,  
         flakeColor  : "#AFDAEF" /* 此处可以定义雪花颜色，若要白色可以改为#FFFFFF */  
     },  
     options = $.extend({}, defaults, options);  
     var interval= setInterval( function(){  
     var startPositionLeft = Math.random() * documentWidth - 100,  
     startOpacity = 0.5 + Math.random(),  
     sizeFlake = options.minSize + Math.random() * options.maxSize,  
     endPositionTop = documentHeight - 200,  
     endPositionLeft = startPositionLeft - 500 + Math.random() * 500,  
     durationFall = documentHeight * 10 + Math.random() * 5000;  
     $flake.clone().appendTo('body').css({  
         left: startPositionLeft,  
         opacity: startOpacity,  
         'font-size': sizeFlake,  
         color: options.flakeColor  
     }).animate({  
         top: endPositionTop,  
        left: endPositionLeft,  
         opacity: 0.2  
     },durationFall,'linear',function(){  
        $(this).remove()  
     });  
     }, options.newOn);  
     };  
 })(jQuery);  
 $(function(){  
     $.fn.snow({   
         minSize: 5, /* 定义雪花最小尺寸 */  
       maxSize: 50,/* 定义雪花最大尺寸 */  
         newOn: 300  /* 定义密集程度，数字越小越密集 */  
    });  
 });